Polyimide x-ray filter substrates optimized for cryogenic temperatures

New generation x-ray instruments for spacecraft such as ASTRO-E and CONSTELLATION-X have very specialized requirements, notably operation at cryogenic temperatures. Luxel Corporation, under a NASA Phase I SBIR contract, undertook the demonstration of feasibility of producing polyimide films suitable for use as x-ray filter substrates specifically optimized for cryogenic applications. 5000 Angstrom thick polyimide films were processed using different cure cycles, and burst pressure (tensile strength) analyses were performed at 293, 77, and 4 Kelvin (K). Test data showed that polyimide films are inherently stronger at cryogenic temperatures than at room temperature (20.5% at 4K). Through cure modification, film strength was increased an additional 9% at 4K over that of the standard cure clearly showing the feasibility of film optimization.